An embodiment relates generally to vision based object detection systems.
Illumination conditions such as shadows can cause errors in the vision based object detection systems. Shadows distort the color of a captured object resulting in ambiguities between (1) edges due to shadows and (2) edges between different entities (e.g., road and landscape). As a result, shadows distort colors of objects and background in the scene leading to appearance of ghost objects and making separation between obstacles and road difficult. Applications have been used to filter out shadows but prior art systems assume the use of a camera having a high quality imager. Cameras with high quality images are expensive with large packaging sizes, and therefore, not practical especially in a mass-produced vehicle based vision system. With the use of high quality imager, the camera sensor is assumed to be narrow-banded and behave like Dirac delta functions in that they have a non-null response only at a single wavelength. However, a low cost imager typically used in vehicle vision based object detection systems does not conform to the narrow-band sensor assumption. Therefore, previous techniques for shadow removal are inapplicable with the use low cost production imagers.